Instrument mounting

ABSTRACT

Structures and/or methods for mounting an instrument housing in a panel cut-out. The instrument housing has flange structure at one end thereof and a plurality of apertures in walls of the housing adjacent the flange structure for the reception of instrument mounting means. The instrument mounting means is comprised of an assembly having a panel engaging portion and a housing engaging portion constructed and arranged so that the panel engaging portion may be inserted through an aperture in a wall of an instrument housing from inside the housing with the instrument housing positioned in a panel cut-out and adjusted to a position whereby the panel is clamped between the panel engaging member of the instrument mounting means and a flange of the housing and the mounting means may be further adjusted to secure it to the housing.

[ 51 Sept. 9, 1975 INSTRUMENT MOUNTING [75] Inventors: Joseph M. Biddle, Center Square;

Paul B. Binder, North Wales, both of Pa.

[73] Assignee: Leeds & Northrup Company, North Wales, Pa.

221 Filed: 0a. 10, 1974 21 Appl. No.: 513,808

2,875,914 3/1959 Buckels... 220/36 2,950,141 8/1960 Koff 85/35 X 3,090,587 5/1963 Peterson 248/27 3,276,834 10/1966 Greenwald et a1. 220/35 X 3,283,937 11/1966 Theodorides 220/36 3,664,615 5/1972 Kruger 248/27 3,746,931 7/1973 Muranaka 248/27 Primary Examiner-J. Franklin Foss Attorney, Agent, or FirmPhilemon J. Moore; Raymond F. MacKay 57] ABSTRACT Structures and/or methods for mounting an instrument housing in a panel cut-out. The instrument housing has flange structure at one end thereof and a plurality of apertures in walls of the housing adjacent the flange structure for the reception of instrument mounting means. The instrument mounting means is comprised of an assembly having a panel engaging portion and a housing engaging portion constructed and arranged so that the panel engaging portion may be inserted through an aperture in a wall of an instrument housing from inside the housing with the instrument housing positioned in a panel cut-out and adjusted to a position whereby the panel is clamped between the panel engaging member of the instrument mounting means and a flange of the housing and the mounting means may be further adjusted to secure it to the housing.

13 Claims, 17 Drawing Figures FIG. 5

HIIFH sum 2 n5 3 lz b PATENTEU 75 IZ'b FIG. 3

FIG.8

FIG.4

FIG.9

PATENTEU SEP 9 75 sum 3 mg 3 INSTRUMENT MOUNTING BACKGROUND OF THE INVENTION 1. Field of the Invention Applicants invention is used for mounting an instrument or instruments in a panel cut-out. Related inventions have been classified in the United States Patent Office with items relating to Measuring and Testing" in a subclass specific to Instrument Casing. Instrument mountings are also to be found in the U.S. Patent Office class relating to Supports, in the subclass enti tled "Instrument In Panel."

2. Description of the Prior Art Many arrangements have been developed over the years for securing an encased instrument in a panel cutout. Most of the arrangements which avoid the use of tapped holes in a panel require means attached to the out-side of an instrument case which effects a clamping engagement between a flange on the front end of an instrument case and a panel. To date, to the best of Applicants knowledge, these arrangements require the installer to have access to the back of the panel. Where large panels are involved and on which there are many instruments and where space in back of a panel is limited or otherwise not easily accessible, the requirement that one have access to the instrument case from the outisde and from the back of the panel is at best inconvenient. U.S. Pat. Nos. 2,440,324; 2,562,260; and 2,766,955 are illustrative of such instrument mountings.

Applicants have devised means and methods whereby an instrument or instruments may be mounted in a panel cut-out by an installer from the front of a panel. In accordance with Applicants invention the application of force to the flange on the front of an instrument housing is automatically limited in a manner which avoids distorting or damaging the flange or any other portion of the housing.

SUMMARY OF THE INVENTION It is an object of Applicants invention to provide an instrument mounting means comprising a bushing and cam assembly. The bushing has a flanged portion of enlarged diameter at one end and an exteriorally threaded portion at the other end. The cam has a threaded passage threadably engaging the threaded portion of the bushing to an extent such that the cam is supported on the bushing in spaced relation with the flanged portion thereof. There is included releasable means tending to hold the cam in fixed position on the bushing. The bushing also includes tool receiving means whereby when an instrument housing having flange structure at the front end thereof is inserted in a panel cut-out and a bushing and cam assembly is positioned in an aperture in a wall of the housing adjacent the flange with a wall portion of the housing disposed between the flanged portion of the bushing and the cam, a tool engaging the tool receiving means may be used to rotate the bushing and cam assembly to cause the cam tightly to engage the panel and draw the flange structure of the housing tightly against the panel and further rotation of the tool overpowering the means tending to hold the cam in fixed position on the bushing thereby to rotate the bushing relative to the cam and draw the cam and the flanged portion of the bushing toward one another to bring the bushing and cam into clamping engagement with the wall portion of the instrument housing.

The aforementioned tool receiving means desirably comprises a passage in the bushing and the passage desirably has associated therewith means for temporarily retaining a tool in the passage. The passage is preferably a hexagonal passage through the bushing coaxial with the longitudinal center line thereof and the means for temporarily retaining a tool is preferably a tool engaging O-ring nested in an internal groove concentrically disposed with respect to the passage. The aforementioned releasable means is desirably an adhesive material disposed in the threaded connection formed by the threadably engaging threaded portion and threaded passage.

It is further an object of Applicants invention to provide an instrument mounting means comprising a box shaped structure including top, bottom, and side walls with panel engaging structure at one end thereof extending outwardly from one or more of the walls, and one or more of the walls including one or more apertures near said one end, the apertures having a size and shape for the cam of a bushing and cam assembly to pass therethrough so the cam may be used for drawing the panel engaging structure of the box shaped structure into engagement with an instrument panel after the box shaped structure has been inserted into a panel cut-out. The apertures will preferably comprise pear shaped holes.

It is more specifically an object of our invention to provide instrument mounting means comprising a box like structure having flange structure at one end thereof and a plurality of pear shaped apertures in walls of said box like structure adjacent the flange structure. A packet is afiixed to the box like structure. The packet contains a plurality of bushing and cam assemblies for insertion in the pear shaped apertures when the box like structure is positioned in a panel cut-out by means of a tool for the purpose of securing the box like structure in the panel cut-out with the flange of the box like structure drawn tightly against the panel by the cams of the bushing and cam assemblies.

It is also an object of our invention to provide a mounting shelf for a plurality of electrical instruments. The shelf comprises a rectangular box like structure having panel engaging structure at one end thereof and a plurality of pear shaped apertures in walls of the box like structure adjacent the panel engaging structure for reception of bushing and cam assemblies for securing the shelf in an opening in an instrument panel, the length, width, and heighth of the box like structure being of such dimensions as to receive a plurality of instrument modules to be mounted on an instrument panel in side-by-side array.

It is still further an object of Applicants invention to provide a new method of mounting an instrument housing on a panel having a cut-out to receive the housing and wherein the housing is provided with panel engaging structure at one end thereof and a plurality of apertures in wall portions of the housing disposed adjacent said one end and wherein the housing is to be secured in the panel cut-out by means of a plurality of fastening assemblies each having a panel engaging portion and a housing engaging portion. The method comprises the steps of positioning the instrument housing in a panel cut-out, inserting the panel engaging portion of one of the fastening assemblies through one of the apertures of the instrument housing, positioning the panel engaging portion of the fastening assembly against the rear face of the panel, urging the panel engaging portion in a direction to draw the panel engaging structure of the instrument housing tightly against the front face of the panel, and while the panel is securely held between the panel engaging structure of the housing and the panel engaging portion of the fastening assembly drawing the panel engaging portion of the fastening assembly and the housing engaging portion of the fastening assembly toward one another into clamping engagement with a wall portion of the housing, and repeating the steps as required adequately to secure the instrument housing to the panel.

Still more specifically it is an object of our invention to provide a method of mounting an instrument housing on a panel having a cut-out to receive the housing and wherein the housing is provided with flange structure and a plurality of apertures disposed adjacent the flange structure and wherein the housing is to be secured in the panel cut-out by means of a plurality of bushing and cam assemblies. The method comprises positioning the instrument housing in a cut-out in a panel with the flange structure of the housing in substantially abutting engagement with the outside of the panel, inserting a tool in the bushing and cam assembly, using part of the tool as a handle guiding the cam of the bushing and cam assembly through one of the apertures in the housing, rotating the cam into engagement with the back of the panel to clamp the panel between the cam and the flange, and rotating the bushing relative to the cam to secure the cam and bushing assembly to the housing, and repeating the steps as required adequately to secure the instrument housing to the panel.

It is another object of Applicants invention to provide in combination an instrument housing having flange structure at one end thereof, a plurality of apertures in walls of the housing adjacent the flange and a plurality of bushing and cam assemblies for securing the housing to a panel having a cut-out to receive the housing, the bushings of each bushing and cam assembly having an external thread cooperating with the internal thread of the cam of the assembly with the cam temporarily fixedly located on the bushing in spaced relation with a flange thereof, and each bushing including tool receiving means whereby after inserting a cam through one of the apertures in the walls of the housing into operative position the cam and bushing assembly may be rotated for clamping a panel between the flange structure of the housing and the cam and upon further rotation of the bushing of said cam and bushing assembly the cam may be drawn toward the flange of the bushing to effect clamping engagement of the cam and bushing with the wall of the instrument housing.

It is broadly speaking an object of our invention to provide in combination an instrument housing having projecting panel engaging structure at one end, an ap-' erture in a wall of said housing disposed adjacent said one end, and an instrument mounting assembly having a panel engaging portion and a housing engaging portion, said aperture being of a shape and size to permit insertion of said panel engaging portion therethrough from inside said housing for disposition of the panel engaging portion on the outside of said housing, means for urging said panel engaging portion in a direction to effect clamping engagement of a panel portion between said projecting panel engaging structure and said panel engaging portion, and means to effect clamping engagement of a portion of said wall of said housing between said panel engaging portion and said housing engaging portion.

BRIEF DESCRIPTION OF THE DRAWINGS For an understanding of Applicants invention the following description and claims should be read with reference to the accompanying drawings wherein:

FIG. I is a rear view in perspective showing an instrument housing mounted in a panel cut-out,

FIG. 2 is a front view in perspective showing an instrument housing mounted in a panel cut-out,

FIG. 3 is a front view in perspective showing a group of instrument housings which differ in size,

FIG. 4 is a rear view in perspective showing a plurality of instrument modules mounted in an instrument housing,

FIG. 5 is a plan view of a mounting assembly in accordance with Applicants invention,

FIG. 6 is a side elevation of the mounting assembly of FIG. 5,

FIG. 7 is a side elevation in section of the mounting assembly of FIG. 3 taken along the line 7-7,

FIG. 8 is a plan view showing an aperture in a wall of an instrument case in accordance with Applicants invention,

FIG. 9 is a side elevation in section taken along the line 9-9 of FIG. 8, and

FIGS. 10- A-H show the steps in a method of mounting an instrument in a panel in accordance with Applicants invention.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1, reference numeral 10 indicates an assembly showing an instrument housing mounted in a cut-out of a panel. The term instrument housing wherever employed in the specification and claims is intended to cover a frame, shelf or box in or onto which an encased instrument may be slid.

In FIG. I a panel I] has a cut-out 11a through which there is slid an instrument housing 12. The housing includes apertures 12a later to be described through which have been inserted panel engaging portions of an instrument mounting assembly for securing the instrument housing to the panel. The instrument mounting assemblies 13 will be described more in detail with reference to other figures of the drawings. In accordance with Applicants invention there may be fastened to the housing 12 as by a tape 14 a packet 15 in the form of a cellophane-bag or other suitable means containing a tool 16 and a plurality of instrument mounting assemblies 13. While in FIG. 1 the packet is shown affixed to case 12 it is to be understood that this is merely used to illustrate the fact that such a packet may be fastened to an instrument housing during shipment of the instwment to a customer and that the packet will be removed prior to installation of the instrument housing into a panel.

In FIG. 2 there is shown a front view of panel 11 having cut-out lla into which there has been inserted an instrument housing 12. This view shows outwardly disposed panel engaging structure 12b in the form of flange structures. While flange structure has been shown it is clearly to be understood that the panel engaging structure may be in the form of interrupted flange like portions, a plurality of individual brackets. pins, or the like. As will be described more fully hereinfter the instrument mounting assembly 13 is shown in the form of a bushing and cam assembly suitable for insertion by an installer using a tool 16 as a handle to insert the instrument mounting assembly through an aperture 120 in the bottom wall of case 12 after the case has been slid into the cut-out in the panel for the purpose of securing the instrument housing to the panel.

In FIG. 3 there is shown a stacked array of instrument housings or shelves 12, 12' and 12" suitable for use in accordance with Applicants invention. The topmost instrument housing 12 desirably includes a pair of holes 12a, one in the top wall and one in the bottom wall (not shown) adjacent the flange 12'b for reception of mounting assemblies 13. While two such holes are desirable only one is essential. The number of holes or apertures is a matter of choice and will depend upon the size of the instrument housing. In accordance with Ap plicants invention the housing 12' may be mounted in a panel cut-out and thereafter an instrument module can be slid in or out of the housing as desired. A second instrument housing 12 is designed to accommodate more than one instrument module, for example, two or three modules. This instrument housing will, of course, be mounted in a panel and permit insertion and withdrawal of a plurality of instrument modules at will. The instrument housing 12" is still larger for use with a greater number of instrument modules such as are shown in FIG. 4.

FIG. 4 is a rear view of an instrument housing 12" showing first, second, third, and fourth instrument modules 17-20 in various stages of insertion into the housing. The module 21 is shown twice the width of the modules 17-20 and may for example be a miniature recorder.

As will be well understood by those skilled in the art, the employment of instrument housings in the form of shelves of various widths provides great flexibility for the mounting of instruments in panel cut-outs with a maximum conservation of panel space. While the instrument housings such as 12, 12' and 12 are shown in the form of shelf-like structures for reception of instrument modules which may be slid in and out like desk drawers and wherein each module is provided with a plurality of apertures such as 12a, l2'a or 12"a and flange elements 12b, l2'b and 12"b which cooperate with instrument mounting assemblies such as 13 for securing the housings to a panel, it is clearly to be understood that instead of using a housing into which an instrument module may be slid the casing of the instrument module itself which contains the instrument may include panel engaging structure such as flange structure 12b or equivalent and apertures such as 12a or equivalent to cooperate with instrument mounting assemblies for securing an instrument to a panel in which case an instrument will not be as readily removable.

In FIG. 5 there is shown a plan view ofa preferred instrument mounting assembly 13 in accordance with Applicants invention. Referring to FIGS. 5, 6, and 7 it may be noted that the mounting assembly 13 includes a cam 22 mounted on the threaded end ofa bushing 23 as by mating threads 2219 and 23b. The bushing 23 includes a flanged, housing engaging portion 23a, a counterbore 23d, and a groove 23a. The portion 23f between the screw thread 23b and the flange 23a is under' cut for sliding engagement into a narrow end of a pear shaped hole in a wall of the housing 12 as later to be described. The bushing 23 includes a hexagonal passage 23c providing a tool receiving means. A suitable tool is an L-shaped hexagonal wrench indicated by reference numeral 16 in FIG. 2 and FIG. 10-A to FIG. l0-H. As later to be described tool 16 is inserted in the hexagonal passage 23c and retained therein by means of an O-ring 26 which is captured in the groove 23e so that when the tool is used as a handle the cam and bushing assembly will be temporarily secured thereto.

The threaded joint 22b, 23b between the cam 22 and the bushing 23 may include an adhesive material such as a LOCTITE sealant available from the LOCTITE Corporation, Newington, Conn., by specifying their product Nutlock 74, so that the cam will be temporarily fixedly located on the bushing in spaced relation with the flange thereof. Such an adhesive will prevent rotation of the cam relative to the bushing until sufficient force is applied to break the seal. Instead of using an adhesive in the threaded connection other means may be used to prevent free relative rotation between cam and bushing. For example the bushing may be slotted and the threaded connection made sufficiently tight to prevent free rotation of the cam relative to the bushing.

In FIGS. 8 and 9 there is illustrated on an enlarged scale one of a plurality of apertures 12a located in wall portions of a housing 12, 12 and 12" adjacent the flange structure 12b. Such apertures located near the front end of the instrument housing adjacent the flange structure 12b are illustrated in FIGS. l4 and FIG. 10-8 to FIG. 10-l-I. As may be seen referring again to FIG. 8, aperture 12a is desirably pear shaped. It has a portion of relatively large diameter adjacent a portion 12d of substantially smaller diameter. While apertures of other shapes may be used the one illustrated has been found satisfactory. The shape of the aperture is such as to permit passage therethrough of both the cam 22 and the flange 23a of the instrument mounting assembly 13. After insertion of one or both of the foregoing elements of the instrument mounting assembly through the aperture 120 the assembly is oriented in a manner such that the cam 22 will lie parallel to and outside of the wall of the housing and the flange 23a inside the housing and the assembly slid sideways into the portion 12d of the aperture 12a so that a portion of the wall of the housing is between the cam 22, which in some of our claims is referred to as panel engaging portion, and the flange 23a which in some of the claims is referred to as a housing engaging portion.

As may be noted by reference to FIG. 9, which is a partial side elevation in section of a portion of the bottom wall of a case 12, the area of the case wall in the region of aperture 12a is depressed forming a bend in the case wall in the area 12e so that upon insertion of an instrument mounting assembly into the aperture 120 the flange 23a of the bushing 23 will not project into the instrument housing. This relationship is best illustrated in FIGS. 10-D and l0-G. From the foregoing it may be understood that the case wall portion surrounding apertures such as 120 in the bottom wall of the case and the top wall of the case will be made to bulge outwardly. While this constructional feature is not always necessary it eliminates projection of any portion of the mounting assembly into the usable volume of the housing and reduces the contact area between the cam 22 and the outside wall of the housing 12 resulting in less friction between the two.

The method of mounting an instrument housing in accordance with Applicants invention is best illustrated by reference to FIGS. l-A to IO-H. While an instrument mounting assembly for example of the bushing and cam type such as 13 may be inserted from outside an instrument housing, if such be convenient, it is designed so that it may be inserted into an instrument housing from inside by an installer working at the front of a panel. To mount an instrument housing or an encased instrument an installer would slide the housing or case into a panel cut-out and position it with the flange in abutting relation with the panel. Thereafter he will place the long leg of the hexagonal wrench 16 in the passage 23c of assembly 13 and push it through the O- ring 26 a distance such that it projects slightly beyond the face of cam 22 as shown in FIG. l0-A. Thereafter he will place the assembled tool and mounting assembly inside case l2 in an aperture 120 in the bottom wall of the housing in a position approximately as shown in FIG. [0-H and insert the mounting assembly through aperture 120 by tilting the wrench toward the front of the housing in a manner such as is illustrated in FIGS. 2 and l0-C. After the assembly 13 has been passed through the aperture 12a with the wrench in a vertical position the flange 23a is drawn upwardly through the enlarged portion 12c of aperture 12a and with the cam 22 outside and the flange 23a inside the case, as shown in FIG. IO-D, the assembly is slid along the aperture so that the undercut portion 23f of bushing 23 is mated with the small diameter portion 12d of aperture 120 as shown in FIG. -E. Thereafter the Allen wrench is ro tated in a direction, (clockwise for the right hand thread), to bring the face of cam 22 into contact with the back of the panel 11. The long leg of the wrench 16 is then withdrawn from assembly 13 and the short leg inserted. The housing should be checked for being properly centered in the panel cut-out then, with the leverage provided by the long leg of the wrench 16, the wrench may be rotated clockwise thereby drawing the flange portion 12b of the housing 12 securely against the panel 1] as shown in FIGS. l0-F and 10-0. As mentioned above, the threaded portion 23b of the bushing 23 in engagement with the threaded portion 22b of the cam 22 is filled with a sealant temporarily to retain the cam 22 in fixed position on the bushing 23. Continued forceful rotation of the wrench 16 in the clockwise direction as shown by the arrow in FIG. l0-H breaks the holding force of the sealant and thereafter permits the bushing to turn in the cam 22 which because of the threaded connection draws the cam 22 toward the flange 23a to bring the flange and cam into clamping engagement with the engaged wall portion of housing 12. As a result the cam is not only locked tightly against the rear wall of the panel but the cam and bushing assembly is likewise securely fastened to the housing 12. After a plurality of instrument mounting assemblies 13 have been installed and secured in apertures of the instrument housing in the manner described above, the instrument housing is securely yet removably mounted in a panel cut-out with all of the work entailed in mounting the instrument being accomplished from in front of the panel. It has been found, for example, that an instrument housing such as FIG. 12" in FIG. 3 when secured to a panel one-quarter inch thick by five cam and bushing assemblies of the type described will support a weight of 200 pounds (90.359 kilograms).

While Applicants have described instrument mounting methods and apparatus for the practice of their invention it is believed evident that the structures may take many forms and still come within the scope of the appended claims.

What is claimed is:

1. An instrument mounting means comprising a bushing and cam assembly,- said bushing having a flanged portion of enlarged diameter at one end and an exteri orally threaded portion at the other end, said cam having a threaded portion threadably engaging said threaded portion of said bushing to an extent such that said cam is supported on said bushing in spaced relation with said flanged portion thereof, releasable means tending to hold said cam in fixed position on said bushing, and said bushing including tool receiving means whereby when an instrument housing having flange structure at the front end thereof is inserted in a panel cut-out and said bushing and cam assembly is positioned inan aperture in a wall of said housing adjacent said flange with a wall portion of said housing disposed between said flanged portion of said bushing and said cam, a tool may be used to rotate said bushing and cam assembly to cause said cam tightly to engage the panel and draw the flange structure of the housing tightly against the panel and upon further rotation of the tool overpower said means tending to hold said cam in fixed position on said bushing thereby to rotate said bushing relative to said cam and draw said cam and said flanged portion of said bushing toward one another to bring said bushing and cam into clamping engagement with the wall portion of said instrument housing.

2. An instrument mounting means in accordance with claim 1 wherein said tool receiving means comprises a passage in said bushing.

3. An instrument mounting means in accordance with claim 2 additionally including means associated with said passage for temporarily retaining a tool in engagement therewith.

4. An instrument mounting means in accordance with claim 3 wherein said passage is a hexagonal passage through said bushing coaxial with the longitudinal center line thereof and said means for temporarily retaining a tool is a tool engaging O-ring nested in an internal groove concentrically disposed with respect to said passage.

5. An instrument mounting means in accordance with claim 1 additionally including means associated with said tool receiving means temporarily to hold a tool in engagement therewith.

6. An instrument mounting means according to claim 1 wherein said releasable means is an adhesive material disposed in the threaded connection formed by said threadably engaging threaded portion and threaded passage.

7. An instrument mounting means comprising a box shaped structure including top, bottom, and side walls, with panel engaging structure at one end thereof extending outwardly from one or more of said walls, and one or more of said walls including one or more pear shaped apertures near said one end, said apertures allowing the bushing of a cam and cam assembly to pass therethrough so the cam may be used for drawing said panel engaging structure into engagement with an instrument panel after said box shaped structure has been inserted into a panel cut-out.

8. An instrument mounting means comprising a box like structure having flange structure at one end thereof, a plurality of pear shaped apertures in walls of said box like structure adjacent said flange structure,

and a packet affixed to said box like structure, said packet containing a plurality of bushing and cam assemblies for inserting in said pear shaped apertures when said box like structure is positioned in a panel cut-out by means of a tool for the purpose of securing said box like structure in said panel cutout with the flange of said box like structure drawn tightly against the panel by the cams of said bushing and cam assemblies,

9. A mounting shelf for a plurality of electrical instruments, said shelf comprising a rectangular box like structure having panel engaging structure at one end thereof and a plurality of pear shaped apertures in walls of said box like structure adjacent said panel engaging structure for reception of bushing and cam assemblies for securing said shelf in an opening in an instrument panel, the length, width and heighth of said box like structure being of such dimensions as to receive a plurality of instrument modules to be mounted on an instrument panel in side-by-side array.

10. A method of mounting an instrument housing on a panel having a cut-out to receive said housing and wherein said housing is provided with panel engaging structure at one end thereof and a plurality of apertures in wall portions of said housing disposed adjacent said one end and wherein said housing is to be secured in said panel cut-out by means of a plurality of fastening assemblies each having a panel engaging portion and a housing engaging portion, said method comprising the steps of positioning said instrument housing in a panel cut-out, inserting the panel engaging portion of one of said fastening assemblies through one of said apertures, positioning said panel engaging portion of said one of said fastening assemblies against the rear face of the panel, urging said panel engaging portion in a direction to draw the panel engaging structure of said housing tightly against the front face of the panel, and while the panel is securely held between said panel engaging structure of said housing and said panel engaging portion of said one of said fastening assemblies drawing the panel engaging portion and the housing engaging portion of said one of said fastening assemblies toward one another into clamping engagement with a wall portion of said housing, and repeating said steps as required adequately to secure said instrument housing on said panel,

11. A method of mounting an instrument housing on a panel having a cutout to receive said housing and wherein said housing is provided with flange structure and a plurality of apertures disposed adjacent said flange structure and wherein said housing is to be secured to said panel cut-out by means of a plurality of bushing and cam assemblies, said method comprising the steps of positioning said instrument housing in a cut-out in a panel with the flange structure of said housing in substantially abutting engagement with the outside of said panel, inserting a tool in said bushing and cam assembly, guiding said cam of said bushing and cam assembly through one of said apertures, rotating said cam into an engagement with the back of said panel to clamp said panel between said cam and said flange, and rotating said bushing relataive to said cam to secure said cam and bushing assembly to said housing.

12. In combination an instrument housing having flange structure at one end thereof, a plurality of apertures in walls of said housing adjacent said flange and a bushing and cam assembly for securing said housing to a panel having a cut-out to receive said housing, the bushing of said cam assembly having an external thread to cooperate with an internal thread of the cam of said bushing and cam assembly with said cam temporarily fixedly related on said bushing in spaced relation with a flange thereof, said bushing including tool receiving means whereby after insertion of said cam into operative position said cam and bushing assembly may be rotated for clamping a panel between the flange structure of said housing and said cam and upon further rotation of said bushing said cam and said flange of said bushing may be drawn together into clamping engagement with the wall of said instrument housing.

13. In combination a housing having projecting panel engaging structure at one end, an aperture in a wall of said housing disposed adjacent said one end, a mounting assembly having a panel engaging portion and a housing engaging portion coupled together for relative motion of one of said portions toward the other of said portions, said aperture being ofa shape and size to permit insertion of said panel engaging portion therethrough from inside said housing for disposition thereof on the outside of said housing, and means for thereafter urging said panel engaging portion in a direction to effect a clamping engagement of a panel portion between said projecting panel engaging structure and said panel engaging portion and for effecting movement of said portions toward each other to produce a clamping engagement of a portion of said wall of said housing between said panel engaging portion and said housing engaging portion. 

1. An instrument mounting means comprising a bushing and cam assembly, said bushing having a flanged portion of enlarged diameter at one end and an exteriorally threaded portion at the other end, said cam having a threaded portion threadably engaging said threaded portion of said bushing to an extent such that said cam is supported on said bushing in spaced relation with said flanged portion thereof, releasable means tending to hold said cam in fixed position on said bushing, and said bushing including tool receiving means whereby when an instrument housing having flange structure at the front end thereof is inserted in a panel cut-out and said bushing and cam assembly is positioned in an aperture in a wall of said housing adjacent said flange with a wall portion of said housing disposed between said flanged portion of said bushing and said cam, a tool may be used to rotate said bushing and cam assembly to cause said cam tightly to engage the panel and draw the flange structure of the housing tightly against the panel and upon further rotation of the tool overpower said means tending to hold said cam in fixed position on said bushing thereby to rotate said bushing relative to said cam and draw said cam and said flanged portion of said bushing toward one another to bring said bushing and cam into clamping engagement with the wall portion of said instrument housing.
 2. An instrument mounting means in accordance with claim 1 wherein said tool receiving means comprises a passage in said bushing.
 3. An instrument mounting means in accordance with claim 2 additionally inclUding means associated with said passage for temporarily retaining a tool in engagement therewith.
 4. An instrument mounting means in accordance with claim 3 wherein said passage is a hexagonal passage through said bushing coaxial with the longitudinal center line thereof and said means for temporarily retaining a tool is a tool engaging O-ring nested in an internal groove concentrically disposed with respect to said passage.
 5. An instrument mounting means in accordance with claim 1 additionally including means associated with said tool receiving means temporarily to hold a tool in engagement therewith.
 6. An instrument mounting means according to claim 1 wherein said releasable means is an adhesive material disposed in the threaded connection formed by said threadably engaging threaded portion and threaded passage.
 7. An instrument mounting means comprising a box shaped structure including top, bottom, and side walls, with panel engaging structure at one end thereof extending outwardly from one or more of said walls, and one or more of said walls including one or more pear shaped apertures near said one end, said apertures allowing the bushing of a cam and cam assembly to pass therethrough so the cam may be used for drawing said panel engaging structure into engagement with an instrument panel after said box shaped structure has been inserted into a panel cut-out.
 8. An instrument mounting means comprising a box like structure having flange structure at one end thereof, a plurality of pear shaped apertures in walls of said box like structure adjacent said flange structure, and a packet affixed to said box like structure, said packet containing a plurality of bushing and cam assemblies for inserting in said pear shaped apertures when said box like structure is positioned in a panel cut-out by means of a tool for the purpose of securing said box like structure in said panel cut-out with the flange of said box like structure drawn tightly against the panel by the cams of said bushing and cam assemblies.
 9. A mounting shelf for a plurality of electrical instruments, said shelf comprising a rectangular box like structure having panel engaging structure at one end thereof and a plurality of pear shaped apertures in walls of said box like structure adjacent said panel engaging structure for reception of bushing and cam assemblies for securing said shelf in an opening in an instrument panel, the length, width and heighth of said box like structure being of such dimensions as to receive a plurality of instrument modules to be mounted on an instrument panel in side-by-side array.
 10. A method of mounting an instrument housing on a panel having a cut-out to receive said housing and wherein said housing is provided with panel engaging structure at one end thereof and a plurality of apertures in wall portions of said housing disposed adjacent said one end and wherein said housing is to be secured in said panel cut-out by means of a plurality of fastening assemblies each having a panel engaging portion and a housing engaging portion, said method comprising the steps of positioning said instrument housing in a panel cut-out, inserting the panel engaging portion of one of said fastening assemblies through one of said apertures, positioning said panel engaging portion of said one of said fastening assemblies against the rear face of the panel, urging said panel engaging portion in a direction to draw the panel engaging structure of said housing tightly against the front face of the panel, and while the panel is securely held between said panel engaging structure of said housing and said panel engaging portion of said one of said fastening assemblies drawing the panel engaging portion and the housing engaging portion of said one of said fastening assemblies toward one another into clamping engagement with a wall portion of said housing, and repeating said steps as required adequately to secure said instrument housing on said panel.
 11. A method of mounting aN instrument housing on a panel having a cut-out to receive said housing and wherein said housing is provided with flange structure and a plurality of apertures disposed adjacent said flange structure and wherein said housing is to be secured to said panel cut-out by means of a plurality of bushing and cam assemblies, said method comprising the steps of positioning said instrument housing in a cut-out in a panel with the flange structure of said housing in substantially abutting engagement with the outside of said panel, inserting a tool in said bushing and cam assembly, guiding said cam of said bushing and cam assembly through one of said apertures, rotating said cam into an engagement with the back of said panel to clamp said panel between said cam and said flange, and rotating said bushing relataive to said cam to secure said cam and bushing assembly to said housing.
 12. In combination an instrument housing having flange structure at one end thereof, a plurality of apertures in walls of said housing adjacent said flange and a bushing and cam assembly for securing said housing to a panel having a cut-out to receive said housing, the bushing of said cam assembly having an external thread to cooperate with an internal thread of the cam of said bushing and cam assembly with said cam temporarily fixedly related on said bushing in spaced relation with a flange thereof, said bushing including tool receiving means whereby after insertion of said cam into operative position said cam and bushing assembly may be rotated for clamping a panel between the flange structure of said housing and said cam and upon further rotation of said bushing said cam and said flange of said bushing may be drawn together into clamping engagement with the wall of said instrument housing.
 13. In combination a housing having projecting panel engaging structure at one end, an aperture in a wall of said housing disposed adjacent said one end, a mounting assembly having a panel engaging portion and a housing engaging portion coupled together for relative motion of one of said portions toward the other of said portions, said aperture being of a shape and size to permit insertion of said panel engaging portion therethrough from inside said housing for disposition thereof on the outside of said housing, and means for thereafter urging said panel engaging portion in a direction to effect a clamping engagement of a panel portion between said projecting panel engaging structure and said panel engaging portion and for effecting movement of said portions toward each other to produce a clamping engagement of a portion of said wall of said housing between said panel engaging portion and said housing engaging portion. 